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Marin Voice: I saved my trees from sudden oak death; you can, too

In the April 14 Marin Master Gardeners feature, “How to get involved in the annual sudden oak death survey,” Martha Proctor wrote, “There are no known methods to arrest the spread of the disease once trees become infected.” She added: “Applying a preventative phosphonate to oaks at risk in the fall is currently the recommended treatment.”

I agree with the second sentence. But regarding the first, that there’s no way to save infected trees, I beg to differ. The answer has long been hiding in plain sight. For more than 20 years I’ve had considerable success saving coast live oaks and tanoaks infected with the fungus (Phytophthora ramorum) that causes sudden oak death, or SOD — trees with the characteristic cankers oozing dark, blood-like sap — as well as preventing healthy trees from becoming infected.

This is what I do. First, I strengthen the immune system of trees with yearly applications of a sprayable potassium phosphite fertilizer like Reliant or Agri-Fos. Second, I amend the pH of soils under tree canopies with calcium, lime, oyster shell dust or related alkaline minerals.